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Investigation of the inherent field-driven charge transport behaviour of three-dimensional lead halide perovskites has largely remained challenging, owing to undesirable ionic migration effects near room temperature and dipolar disorder instabilities prevalent specifically in methylammonium-and-lead-based high-performing three-dimensional perovskite compositions. Here, we address both these challenges and demonstrate that field-effect transistors based on methylammonium-free, mixed metal (Pb/Sn) perovskite compositions do not suffer from ion migration effects as notably as their pure-Pb counterparts and reliably exhibit hysteresis-free p-type transport with a mobility reaching 5.4 cm2 V-1 s-1. The reduced ion migration is visualized through photoluminescence microscopy under bias and is manifested as an activated temperature dependence of the field-effect mobility with a low activation energy (~48 meV) consistent with the presence of the shallow defects present in these materials. An understanding of the long-range electronic charge transport in these inherently doped mixed metal halide perovskites will contribute immensely towards high-performance optoelectronic devices.

Point-defect engineering is an effective way to control the mobility and transparent-conducting performance of sputtered fluorine-doped ZnO (FZO) thin films. In this study, doping with fluorine (F) is accomplished through a simple one-step deposition process and is demonstrated to enhance the crystal quality, eliminate the point defects, and boost the mobility as well as the performance of the films. Furthermore, the films’ characteristics are observed to be strongly dependent on F content. At the optimum F content of 1%, the FZO films exhibited the best crystal quality and the lowest concentration of Zn interstitial and O vacancy defects due to F passivation. Moreover, a mobility as high as 45.3 cm2/V and the greatest figure-of-merit performance are achieved for cutting-edge transparent electrode applications. However, a further increase of F content brought about an increased concentration of defects relating to Zn vacancies, especially F interstitials, which yielded the low mobility and poor performance due to the degraded structure.

In this paper, we present an mmWave-based vehicle-to-infrastructure (V2I) communication system operating at a $22-23 \textrm {GHz}$ frequency band, and evaluate its feasibility and effectiveness on an actual highway through a field trial. Based on a network layout that is well suited for the mmWave-based high mobility vehicular applications, we provide physical and higher layer design details, which are based on the 3GPP 5G New Radio (NR) standard. We then investigate key technologies to overcome the performance degradation of the mmWave-based system due to high mobility: a user equipment (UE)-oriented beam switching-based beamforming scheme, a fast and robust handover procedure with a two-step timing advance (TA) update, and mobile relaying for providing better quality-of-service (QoS) to in-vehicle UEs. The proposed system design and related key technologies are validated through a real-world testbed in an actual highway test site. Regarding this, we describe the specifics of testbed implementation and provide the experimental results obtained from the trial. The validation results show that the 5G NR-based mmWave system is feasible and effective for realizing high data rate vehicular communication on a highway.

The lack of a sizeable band gap has so far prevented graphene from building effective electronic and optoelectronic devices despite its numerous exceptional properties. Intensive theoretical research reveals that a band gap larger than 1 eV can only be achieved in sub-3 nm wide graphene nanoribbons (GNRs), but real fabrication of such ultranarrow GNRs still remains a critical challenge. Herein, we demonstrate an approach for the synthesis of ultranarrow and photoluminescent semiconducting GNRs by longitudinally unzipping single-walled carbon nanotubes. Atomic force microscopy reveals the unzipping process, and the resulting 2.2 nm wide GNRs are found to emit strong and sharp photoluminescence at ∼685 nm, demonstrating a very desirable semiconducting nature. This band gap of 1.8 eV is further confirmed by follow-up photoconductivity measurements, where a considerable photocurrent is generated, as the excitation wavelength becomes shorter than 700 nm. More importantly, our fabricated GNR field-effect transistors (FETs), by employing the hexagonal boron nitride-encapsulated heterostructure to achieve edge-bonded contacts, demonstrate a high current on/off ratio beyond 105 and carrier mobility of 840 cm2/V s, approaching the theoretical scattering limit in semiconducting GNRs at room temperature. Especially, highly aligned GNR bundles with lengths up to a millimeter are also achieved by prepatterning a template, and the fabricated GNR bundle FETs show a high on/off ratio reaching 105, well-defined saturation currents, and strong light-emitting properties. Therefore, GNRs produced by this method open a door for promising applications in graphene-based electronics and optoelectronics.

Hydrogenated polycrystalline In2O3 (In2O3:H) thin-film transistors (TFTs) fabricated via the low-temperature solid-phase crystallization (SPC) process with a field-effect mobility (μFE) exceeding 100 cm2 V−1 s−1 are promising candidates for future electronics applications. In this study, we investigated the effects of the SPC temperature of Ar + O2 + H2-sputtered In2O3:H films on the electron transport properties of In2O3:H TFTs. The In2O3:H TFT with an SPC temperature of 300 °C exhibited the best performance, having the largest µFE of 139.2 cm2 V−1 s−1. In contrast, the µFE was slightly degraded with increasing SPC temperature (400 °C and higher). Extended X-ray absorption fine structure analysis revealed that the medium-range ordering in the In2O3:H network was further improved by annealing up to 600 °C, while a large amount of H2O was desorbed from the In2O3:H films at SPC temperatures above 400 °C, resulting in the creation of defects at grain boundaries. The threshold temperature of H2O desorption corresponded well with the carrier transport properties; the µFE of the TFTs started to deteriorate at SPC temperatures of 400 °C and higher. Thus, it was suggested that the hydrogen remaining in the film after SPC plays an important role in the passivation of electron traps, especially for grain boundaries, resulting in an enhancement of the µFE of In2O3:H TFTs.

Enhancement-mode 4H-SiC MOSFETs utilising an aluminium oxide (Al2O3) dielectric without the requirement for an underlying silicon oxide (SiO2) layer have been shown to have a field effect mobility of 150 cm2V−1s−1 and a subthreshold swing of 160 mV/dec. The fabricated devices utilised a forming gas (3% H2 in N2) anneal immediately prior to the deposition of the Al2O3 by Atomic Layer Deposition (ALD). A comparison MOSFET using an identical Al2O3 deposition process with a 0.7 nm SiO2 layer had a field effect mobility of approximately 20 cm2V−1s−1. The hydrogen annealed device had a lower density of interface traps (Dit), a lower subthreshold swing, and a significantly reduced hysteresis in the transconductance data than the thin SiO2 sample. This finding solves the issue of inconsistency of device performance using thin film gate dielectric as an interfacial layer by offering a simple and controllable process.

In quantizing magnetic fields, graphene superlattices exhibit a complex fractal spectrum often referred to as the Hofstadter butterfly. It can be viewed as a collection of Landau levels that arise from quantization of Brown-Zak minibands recurring at rational ($p/q$) fractions of the magnetic flux quantum per superlattice unit cell. Here we show that, in graphene-on-boron-nitride superlattices, Brown-Zak fermions can exhibit mobilities above 10$^6$ cm$^2$V$^{-1}$s$^{-1}$ and the mean free path exceeding several micrometers. The exceptional quality of our devices allows us to show that Brown-Zak minibands are $4q$ times degenerate and all the degeneracies (spin, valley and mini-valley) can be lifted by exchange interactions below 1K. We also found negative bend resistance at $1/q$ fractions for electrical probes placed as far as several micrometers apart. The latter observation highlights the fact that Brown-Zak fermions are Bloch quasiparticles propagating in high fields along straight trajectories, just like electrons in zero field., 16 pages, 13 figures

Graphene offers many useful properties that can revolutionize modern electronic devices. Specifically, it provides high charge carrier mobility in a mechanically robust, atomically thin form factor. Many of these properties are observed in graphene which is prepared from exfoliated graphite and processed with electron beam lithography. These processes are both time intensive and cost- prohibitive for the large-scale production necessary for use in consumer electronics. This work details the processing and characterization of commercially available graphene from chemical vapor deposition (CVD) on SiO2/Si and on hBN-layered SiO2/Si wafers using conventional photolithography on the 4″ wafer standard. The findings indicate that the CVD graphene films are resilient after processing even for lengths up to 1 mm. Electrical characterization via resistance measurements and the Hall Effect at room temperature clearly indicates the influence of the substrate material on the graphene’s electrical properties. At these length scales, graphene on SiO2 resembles that of a lightly doped semiconductor in terms of its carrier density (7.8 × 1015 cm−2), yet its carrier mobility (2.6 cm2/Vs) resembles that of a metal. Graphene on hBN/SiO2 has a carrier density of 8.2 × 1012 cm−2 and carrier mobility of 2.68 × 103 cm2/Vs—comparable to existing high-mobility semiconducting materials. CVD graphene and conventional photolithography does provide a cost-effective means for producing large form-factor graphene devices for low to moderate mobility applications and eventually for large-scale monolithic graphene electronics.

This paper reports the effect of the cation composition on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) where atomic layer deposition (ALD) was used to deposit an a-IGZO channel layer. The In0.38Ga0.18Zn0.44O transistors at a 200°C annealing temperature exhibited 39.4 cm2/V·s field effect mobility (µFE), −0.12 V threshold voltage (VTH), 0.40 V/decade subthreshold gate swing (SS), and >107 ION/OFF ratio, corresponding to the state-of-the-art characteristics of transistors with a sputtered IGZO channel. Further enhancement of the μFE value was observed for the devices with a higher In fraction: the In0.45Ga0.15Zn0.40O transistor had a higher μFE value of 48.3 cm2/V·s, −4.06 V VTH, 0.45 V/decade SS, and >107 ION/OFF ratio. The cation composition dependence on the performance of the a-IGZO TFTs was explained by analysing the density-of-state (DOS) distribution for the corresponding devices using the experimental independent variable (IV) and theoretical Technology Computer-aided Design (TCAD) simulation.

The ever increasing requirements in wireless communications have led to the search for unexploited correlations that could improve channel estimation and tracking. Kalman filtering (KF) has been proposed to exploit several such correlations, e.g., the time correlation in each tap in a multi-path channel. When making full use of this correlation, however, a capital disadvantage of KF is its weak performance in the face of a significant, occasional nonlinearity, such as the potential birth of a new tap in a multipath channel or an active tap's death. These nonlinearities are typical for vehicular applications. So far, solutions proposed to this birth-death nonlinearity problem have been shown to be computationally prohibitive. In this paper, a simplified detection framework is introduced and a computationally inexpensive simplified maximum a posteriori estimator is derived. Under low to medium SNR conditions, simulations show the channel tracking error can be approximately halved (versus simple KF) by this novel estimator in orthogonal frequency division multiplexing systems.

Recent studies on organic thin-film transistors (OTFTs) have reported high mobility values, but many of them showed non-ideal current–voltage characteristics that could lead to the overestimation of the mobility values. In this study, the non-ideal transistor behavior was briefly investigated by considering the effect of charge injection, and a method of overcoming the effect was developed. Correspondingly, various charge injection layers were developed, and their effects on the modification of metal contacts, including work function tuning and interfacial doping, were studied. The materials that had been coated formed a good metal-semiconductor interface through fine manipulation in the wetting and dewetting of the selected liquid. With such electrodes, the OTFTs were fabricated at room temperature and exhibited almost ideal transistor behavior in terms of the current–voltage characteristics, featuring high (over 10 cm2/Vs) field-effect mobility.

In this paper, we report on the structural and electronic properties of polycrystalline gallium antimonide (poly-GaSb) films (50–250 nm) deposited on p+ Si/SiO2 by metalorganic vapour phase epitaxy at 475 °C. GaSb films grown on semi-insulating GaAs substrates are included as comparative samples. In all cases, the unintentionally doped GaSb is p-type, with a hole concentration in the range of 2 × 1016 to 2 × 1017 cm−3. Exceptional hole mobilities are measured for polycrystalline GaSb on SiO2 in the range of 9–66 cm2/Vs, exceeding the reported values for many other semiconductors grown at low temperatures. A mobility of 9.1 cm2/Vs is recorded for an amorphous GaSb layer in a poly-GaAs/amorphous GaSb heterostructure. Mechanisms limiting the mobility in the GaSb thin films are investigated. It is found that for the GaSb grown directly on GaAs, the mobility is phonon-limited, while the GaSb deposited directly on SiO2 has a Coulomb scattering limited mobility, and the poly-GaAs/amorphous GaSb heterostructure on SiO2 displays a mobility which is consistent with variable-range-hopping. GaSb films grown at low temperatures demonstrate a far greater potential for implementation in p-channel devices than for implementation in ICs.

Providing stable and fast data transmission service is challenging in a high mobility wireless communication system, where massive multiple-input multiple-output (MIMO) beamforming is deemed as a potential solution. In the literature, the majority of previous works focused on how to optimize the beamforming scheme with traditional side information like perfect or imperfect channel state information (CSI) in non-mobile or low mobility scenarios. However, it is hard to either track the channel or obtain perfect CSI in the high mobility scenario without large online computation, because the wireless channel appears to be fast time varying and double-selective in the spatial-temporal domain. In this paper, by exploiting the special characters in the high mobility scenario, we introduce an applicable low-complexity beamforming scheme with transmit diversity in the high mobility scenario with the aid of location information. The beam is generated and selected mainly based on the location information, where the beam weight is optimized to maximize the total service that one BS can provide. Moreover, to guarantee a full diversity gain in this joint scheme, an optimal beam selection algorithm is proposed. Besides, to maximize the total service competence of one base station, a closed-form power allocation solution for the multi-user scenario is derived. To solve the potential inter-beam interference in massive MIMO system, a location-aided algorithm is proposed to eliminate the interference and maximize the mobile service of the whole train at the same time. Theoretical analysis and multiple simulation results show that our scheme approaches the theoretical performance bound of adaptive beamforming scheme but with much lower complexity.

In this paper, we demonstrate high-mobility inkjet-printed indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) using a solution-processed Sr-doped Al2O3 (SAO) gate dielectric. Particularly, to enhance to the electrical properties of inkjet-printed IGZO TFTs, a linear-type printing pattern was adopted for printing the IGZO channel layer. Compared to dot array printing patterns (4 × 4 and 5 × 5 dot arrays), the linear-type pattern resulted in the formation of a relatively thin and uniform IGZO channel layer. Also, to improve the subthreshold characteristics and low-voltage operation of the device, a high-k and thin (~10 nm) SAO film was used as the gate dielectric layer. Compared to the devices with SiO2 gate dielectric, the inkjet-printed IGZO TFTs with SAO gate dielectric exhibited substantially high field-effect mobility (30.7 cm2/Vs). Moreover, the subthreshold slope and total trap density of states were also significantly reduced to 0.14 V/decade and 8.4 × 1011/cm2·eV, respectively.

Copper oxide (CuxO) films are considered to be an attractive hole-transporting material (HTM) in the inverted planar heterojunction perovskite solar cells due to their unique optoelectronic properties, including intrinsic p-type conductivity, high mobility, low-thermal emittance, and energy band level matching with the perovskite (PS) material. In this study, the potential of reactive sputtered CuxO thin films with a thickness of around 100 nm has been extensively investigated as a promising HTM for effective and stable perovskite solar cells. The as-deposited and annealed films have been characterized by using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Photoluminescence (PL), UV-Vis spectroscopy, and Hall-effect measurement techniques. The significant change in structural and optoelectronic properties has been observed as an impact of the thermal annealing process. The phase conversion from Cu2O to CuO, including grain size increment, was observed upon thermal annealing. The transmittance and optical bandgap were found to vary with the films’ crystallographic transformation. The predominant p-type conductivity and optimum annealing time for higher mobility have been confirmed from the Hall measurement. Films’ optoelectrical properties were implemented in the complete perovskite solar cell for numerical analysis. The simulation results show that a 40 min annealed CuxO film yields the highest efficiency of 22.56% with a maximum open-circuit voltage of 1.06 V.

We utilized Ni as a floating capping layer in p-channel SnO thin-film transistors (TFTs) to improve their electrical performances. By utilizing the Ni as a floating capping layer, the p-channel SnO TFT showed enhanced mobility as high as 10.5 cm2·V−1·s−1. The increase in mobility was more significant as the length of Ni capping layer increased and the thickness of SnO active layer decreased. The observed phenomenon was possibly attributed to the changed vertical electric field distribution and increased hole concentration in the SnO channel by the floating Ni capping layer. Our experimental results demonstrate that incorporating the floating Ni capping layer on the channel layer is an effective method for increasing the field-effect mobility in p-channel SnO TFTs.

Low-dimensional high-quality InSb materials are promising candidates for next-generation quantum devices due to the high carrier mobility, low effective mass, and large g-factor of the heavy element compound InSb. Various quantum phenomena are demonstrated in InSb 2D electron gases and nanowires. A combination of the best features of these two systems (pristine nanoscale and flexible design) is desirable to realize, e.g., the multiterminal topological Josephson device. Here, controlled growth of 2D nanostructures, nanoflakes, on an InSb platform is demonstrated. An assembly of nanoflakes with various dimensions and morphologies, thinner than the Bohr radius of InSb, are fabricated. Importantly, the growth of either nanowires or nanoflakes can be enforced experimentally by setting growth and substrate design parameters properly. Hall bar measurements on the nanostructures yield mobilities up to ≈20 000 cm 2 V −1 s −1 and detect quantum Hall plateaus. This allows to see the system as a viable nanoscale 2D platform for future quantum devices.

Over the past years, thermoelectric Mg3Sb2 alloys particularly in n‐type conduction, have attracted increasing attentions for thermoelectric applications, due to the multivalley conduction band, abundance of constituents, and less toxicity. However, the high vapor pressure, causticity of Mg, and the high melting point of Mg3Sb2 tend to cause the inclusion in the materials of boundary phases and defects that affect the transport properties. In this work, a utilization of tantalum‐sealing for melting enables n‐type Mg3Sb2 alloys to show a substantially higher mobility than ever reported, which can be attributed to the purification of phases and to the coarse grains. Importantly, the inherently high mobility successfully enables the thermoelectric figure of merit in optimal compositions to be highly competitive to that of commercially available n‐type Bi2Te3 alloys and to be higher than that of other known n‐type thermoelectrics at 300–500 K. This work reveals Mg3Sb2 alloys as a top candidate for near‐room‐temperature thermoelectric applications.

The crystallisation of sputter-deposited, amorphous In2O3:H films was investigated. The influence of deposition and crystallisation parameters onto crystallinity and electron hall mobility was explored. Significant precipitation of metallic indium was discovered in the crystallised films by electron energy loss spectroscopy. Melting of metallic indium at ~160 °C was suggested to promote primary crystallisation of the amorphous In2O3:H films. The presence of hydroxyl was ascribed to be responsible for the recrystallization and grain growth accompanying the inter-grain In-O-In bounding. Metallic indium was suggested to provide an excess of free electrons in as-deposited In2O3 and In2O3:H films. According to the ultraviolet photoelectron spectroscopy, the work function of In2O3:H increased during crystallisation from 4 eV to 4.4 eV, which corresponds to the oxidation process. Furthermore, transparency simultaneously increased in the infraredspectral region. Water was queried to oxidise metallic indium in UHV at higher temperature as compared to oxygen in ambient air. Secondary ion mass-spectroscopy results revealed that the former process takes place mostly within the top ~50 nm. The optical band gap of In2O3:H increased by about 0.2 eV during annealing, indicating a doping effect. This was considered as a likely intra-grain phenomenon caused by both (In0)O•• and (OH−)O• point defects. The inconsistencies in understanding of In2O3:H crystallisation, which existed in the literature so far, were considered and explained by the multiplicity and disequilibrium of the processes running simultaneously.

International audience; Forecast Scheduling (FS) is a scheduling concept that utilizes rate prediction along the users' trajectories in order to optimize the scheduler allocation. The rate prediction is based on Signal to Interference plus Noise Ratio (SINR) or rate maps provided by a Radio Environment Map (REM). The FS has been formulated as a convex optimization problem namely the maximization of an α−fair utility function of the cumulated rates of the users along their trajectories [1]. This paper proposes a fast heuristic for the FS problem based on two FS users' scheduling. Furthermore, it is shown that in the case of two users, the FS problem can be solved analytically, making the heuristic computationally very efficient. Numerical results illustrate the throughput gain brought about by the scheduling solution.

International audience; Recent developments in transport systems and information technology applications enable people to move more frequently, faster, and further afield. The increasing flexibility of the labour market requires these new potentials to be pressed into use, with increased mobility as a result. Specific high mobility practices are emerging, such as daily long-duration commuting, weekly commuting and work-related frequent trips. However, people are not equal regarding high mobility. Based on the quantitative study Job Mobilities and Family Lives conducted in 2007 and 2011, this article combines longitudinal and cross-sectional perspectives to explore the potential of individuals for (high) mobility, using the concept of “motility”. Results show that motility is able to explain to a significant extent the various situations regarding a possible resort to high mobility. Although some of the participants are in a good position to cope with high mobility, others combine poor access to mobility and poor mobility skills. Even if they declare being ready to move, they appear to be a vulnerable position. Further results show that the evolution of mobility potential is explained by changes in mobility projects: family, economic and spatial contexts are central to a better understanding of these changes. In this regard, the situation of the Spaniards, particularly affected from 2008 by the financial crisis, is striking. Finally, analysis of the link between motility and mobility underlines that a higher mobility potential often does not imply more frequent resort to high mobility.; Le développement des offres en matière de transports et de technologies de la communication permettent aux personnes de se déplacer toujours plus, plus loin et plus rapidement. La flexibilisation du marché du travail impose l’utilisation de ces potentiels et favorise la mobilité. Plus spécifiquement, elle accompagne l’émergence de pratiques de grande mobilité, telles que la pendularité de longue durée, la bi-résidentialité ou encore les voyages fréquents pour motif professionnel. Dans ce contexte, les personnes ne sont pas toutes égales face à la grande mobilité. Basé sur l’enquête quantitative longitudinale Job Mobilities and Family Lives réalisée en 2007 puis en 2011, cet article, dans une perspective transversale et longitudinale, vise à explorer le potentiel de (grande) mobilité des personnes, à l’aide du concept de « motilité ». Premièrement, les résultats montrent que la motilité permet de décrire finement les situations des personnes dans la perspective d’un recours éventuel à la grande mobilité. Alors que certains sont dans une position confortable face à la grande mobilité, d’autres en revanche combinent de mauvaises compétences de mobilité et des accès limités. Même s’ils se déclarent disposés à la grande mobilité, ils apparaissent comme plus vulnérables. Deuxièmement, l’évolution du potentiel de mobilité est avant tout portée par des changements dans les projets de mobilité : les contextes familiaux, économiques et spatiaux dans lesquels les personnes se trouvent expliquent ces changements. La situation des Espagnols, particulièrement touchés par la crise dès 2008, est à ce sujet très parlante. Finalement, l’analyse du lien entre motilité et mobilité montre, de manière contre-intuitive, qu’un plus grand potentiel de mobilité ne se traduit pas nécessairement par un recours plus important à la grande mobilité.

The increase of rated voltages for modern HVDC polymeric cables up to about 400 kV, thanks to high performance insulating materials and higher design fields, may raise long-term reliability concerns due to space charge accumulation. In particular, heterocharge build up can enhance locally the electric field at the electrode/insulation interface. Use of Voltage Source Converters (VSC), which do not permit polarity inversions, allows a limited amount of injected charge to be tolerated, but only if it leads to homocharge accumulation. However, if injected charge migrates towards the opposite electrode and extraction is delayed, heterocharge can build up, thus affecting eventually electrical insulation. This paper shows that at electric field values of 20-40 kV/mm, i.e. in the range of cable design fields, small charge packets, injected from the electrodes and crossing the insulation very fast as coherent charge pulses, can lead to significant heterocharge accumulation in the presence of a partially-blocking electrode. Even in the absence of a noticeable heterocharge accumulation, the electric field perturbation caused by each charge pulse can provide a non-negligible life reduction of cable insulation. Therefore, the development of proper techniques able to detect and analyze these fast pulses is of utmost importance not only for scientific reasons, but also for design and reliability issues.

During the 1920 Haiyuan earthquake, numerous catastrophic landslides were triggered in the loess area in Northwest China. We investigated in detail a large example of these landslides, referred to as Dangjiacha landslide in this paper. This landslide originated from a slope of about 20°, and the displaced soil mass traveled about 3200 m, damming a valley. We performed a field survey and found that standing water existed in the landslide area and the loess had high porosity. We infer that it was the liquefaction of the water-saturated loess layer rather than the suspension of silt in the pore-air in the loess that caused the great mobility of this landslide. To test this inference, we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water. The test results showed that the water-saturated loess soil was highly susceptible to flow liquefaction failure. Fast shear tests on naturally air-dried loess samples revealed that the generated pore-air pressure was small under the “undrained condition” and no significant reduction in the shear resistance was observed, implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large-scale landslide.

Over the past years, thermoelectric Mg3Sb2 alloys particularly in n‐type conduction, have attracted increasing attentions for thermoelectric applications, due to the multivalley conduction band, abundance of constituents, and less toxicity. However, the high vapor pressure, causticity of Mg, and the high melting point of Mg3Sb2 tend to cause the inclusion in the materials of boundary phases and defects that affect the transport properties. In this work, a utilization of tantalum‐sealing for melting enables n‐type Mg3Sb2 alloys to show a substantially higher mobility than ever reported, which can be attributed to the purification of phases and to the coarse grains. Importantly, the inherently high mobility successfully enables the thermoelectric figure of merit in optimal compositions to be highly competitive to that of commercially available n‐type Bi2Te3 alloys and to be higher than that of other known n‐type thermoelectrics at 300–500 K. This work reveals Mg3Sb2 alloys as a top candidate for near‐room‐temperature thermoelectric applications.

A high‐mobility p‐type organic semiconductor based on benzodithiophene and diketopyrrolopyrrole with linear alkylthio substituents (BDTS‐2DPP) is used as a dual function interfacial layer to modify the interface of perovskite/2,2′,7,7′‐tetrakis(N,N′‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene in planar perovskite solar cells. The BDTS‐2DPP layer can remarkably passivate the surface defects of perovskite through the formation of Lewis adduct between the under‐coordinated Pb atoms in perovskite and S atoms in BDTS‐2DPP, and also shows efficient hole extraction and transfer properties. The devices with BDTS‐2DPP interlayer show a peak power conversion efficiency of 18.2%, which is higher than that of reference devices without the BDTS‐2DPP interlayer (16.9%). Moreover, the hydrophobic BDTS‐2DPP interlayer effectively protects the perovskite against moisture, leading to enhanced device stability.

We use ab initio density-functional calculations to determine the interaction of a graphene monolayer with the Si(111) surface. We find that graphene forms strong bonds to the bare substrate and accommodates the 12% lattice mismatch by forming a wavy structure consisting of free-standing conductive ridges that are connected by ribbon-shaped regions of graphene, which bond covalently to the substrate. We perform quantum transport calculations for different geometries to study changes in the transport properties of graphene introduced by the wavy structure and bonding to the Si substrate. Our results suggest that wavy graphene combines high mobility along the ridges with efficient carrier injection into Si in the contact regions. DOI: 10.1103/PhysRevLett.110.176805

Consider a centralized query operator that identifies to every smart phone user its k geographically nearest neighbors at all times, a query we coin Continuous All k-Nearest Neighbor (CAkNN). Such an operator could be utilized to enhance public emergency services, allowing users to send SOS beacons out to the closest rescuers and allowing gamers or social networking users to establish ad-hoc overlay communication infrastructures, in order to carry out complex interactions. In this paper, we study the problem of efficiently processing a CAkNN query in a cellular or WiFi network, both of which are ubiquitous. We introduce an algorithm, coined Proximity, which answers CAkNN queries in O(n(k+λ)) time, where n denotes the number of users and λ a network-specific parameter (λ ≪ n). Proximity does not require any additional infrastructure or specialized hardware and its efficiency is mainly attributed to a smart search space sharing technique we introduce. Its implementation is based on a novel data structure, coined k+-heap, which achieves constant O(1) look-up time and logarithmic O(log(k*λ .)) insertion/update time. Proximity, being parameter-free, performs efficiently in the face of high mobility and skewed distribution of users (e.g., the service works equally well in downtown, suburban, or rural areas). We have evaluated Proximity using mobility traces from two sources and concluded that our approach performs at least one order of magnitude faster than adapted existing work. © 2012 IEEE. 79 88 Sponsors: IBM MICS Indian Institute of Technology Microsoft Research Bell Labs Conference code: 94301 Cited By :18

Highlights ► n-Type C60 organic field effect transistors optimized for low voltage operation. ► Thin parylene-C films are employed as dielectric layers. ► Metal oxides capped with organic films lead to optimized dielectric properties. ► Mobilities in the range of 3 cm2 V−1 s−1 are possible at operating voltages below 1 V., We report on C60 based organic field effect transistors (OFETs) that are well optimized for low voltage operation. By replacing commonly used dielectric layers by thin parylene films or by utilizing different organic materials like divinyltetramethyldisiloxane-bis(benzocyclo-butene) (BCB), low density polyethylene (PE) or adenine in combination with aluminum oxide (AlOx) to form a bilayer gate dielectric, it was possible to significantly increase the capacitance per unit area (up to two orders of magnitude). The assembly of metal-oxide and organic passivation layer combines the properties of the high dielectric constant of the metal oxide and the good organic–organic interface between semiconductor and insulator provided by a thin capping layer on top of the AlOx film. This results in OFETs that operate with voltages lower than 500 mV, while exhibiting field effect mobilities exceeding 3 cm2 V−1 s−1.

Magnetoconductance of a gated two-dimensional electron gas (2DEG) in the inversion layer on p-type HgCdTe crystal is investigated. At strong magnetic fields, characteristic features such as quantum Hall effect of a 2DEG with single subband occupation are observed. At weak magnetic fields, weak antilocalization effect in ballistic regime is observed. Phase coherence time and zero-field spin-splitting are extracted according to Golub's model. The temperature dependence of dephasing rate is consistent with Nyquist mechanism including both singlet and triplet channel interactions., Comment: submit to prb

Vehicular ad hoc networks have emerged recently as a platform to support intelligent inter-vehicle communication and improve traffic safety and performance. The road-constrained and high mobility of the vehicles, their unbounded power source, and the emergence of roadside wireless infrastructures make VANETs a challenging research topic. A key to the development of protocols for intervehicle communication and services lies in the knowledge of the topological characteristics of the VANET communication graph. This article provides answers to the general question: how does a VANET communication graph look like over time and space? This study is the first one that examines a very large-scale VANET graph and conducts a thorough investigation of its topological characteristics using several metrics, not examined in previous studies. Our work characterizes a VANET graph at the connectivity (link) level, quantifies the notion of "qualitative" nodes as required by routing and dissemination protocols, and examines the existence and evolution of communities (dense clusters of vehicles) in the VANET. Several latent facts about the VANET graph are revealed and incentives for their exploitation in protocol design are examined. 502 511 Sponsors: IEEE ACM Imperial College London HP IBM Conference code: 79368 Cited By :40

As currently specified by 3GPP, MBMS (Multimedia Broadcast Multicast Service) content can be provided in a cell by either Point-to-Point (P-t-P) or Point-to-Multipoint (P-t-M) transmission mode, but not both at the same time. In earlier work we highlighted the deficiencies of the current approach and proposed the concept of the "Dual transmission mode cell", in which P-t-P (DCH) and P-t-M (FACH) transmissions can coexist and allowed to dynamically adapt through time, to address them. In this paper we further analyze the deficiencies of the current 3GPP approach and enhance our previous work to efficiently address the problem in high mobility scenarios as well. The proposed algorithm takes into consideration both the distribution and the movement of the MBMS users' within the cell (using the CPICH Ec/No signal strength as a reference) and dynamically decides which MBMS users should be served using FACH and which should be served using DCH. Simulation results show significant transmission power savings, considerable reduction on the aggregated signaling and processing effort introduced, while QoS requirements are still fulfilled. © 2008 IEEE. Conference code: 77039 Cited By :1

A recent study of the decay of microwave-induced resistance oscillations (MIRO) in GaAs/AlGaAs quantum wells due to an in-plane magnetic field B ∥ has revealed the dominant role of a quadratic-in-B ∥ correction to the quantum scattering rate. In the present study, we examine the evolution of Shubnikov-de Haas oscillations (SdHO) with increasing tilt angle in the same sample. Even though we find that the SdHO also diminish at high tilt angles, this decay is qualitatively different from that of MIRO, possibly indicating a different physical origin., 20th International Conference on the Application of High Magnetic Fields in Semiconductor Physics, HMF 2012, July 22-27, 2012, Chamonix Mont Blanc

The study presents the issue of kinematic discrepancy of hydrostatic drive systems of high mobility vehicles, and its impact on the presence of the unfavourable phenomenon of circulating power. Furthermore, it presents a theoretical discussion concerning the capacity of the compensation of kinematic discrepancy by a hydrostatic drive system on the basis of tests using static characteristics.

Commuting and travelling extensively for job reasons both helps and challenges people to balance competing demands of work and personal life. People do not have equal resources and possibilities to benefit from high mobility. Globalisation, labour flexibility and insecurity, transport and telecommunications systems have led to more complex, more personalised and more fluctuating mobile living arrangements. Moreover, work-related travel has not only to do with occupations and careers, but must be understood in relation with the broader context (spatial, residential, cultural, political, economic and relational) in which people are embedded (Mandersheid, 2013, Sheller & Urry, 2006). While social scientists have paid increasing attention to this area in the last 15 years, previous longitudinal studies have mainly focused on migration and residential mobility, neglecting other forms of movement. This talk brings together ideas and findings from our forthcoming book ‘High Mobility in Europe: balancing work and personal life’ (Palgrave Macmillan). It explores how high mobility behaviours and their relations to personal life change over the life course. Mixed methods were used based on two-wave panel data and retrospective data collected in four European countries (France, Germany, Spain and Switzerland) from the research project ‘Job Mobilities and Family Lives in Europe’ (Schneider and Meil, 2008). Particular emphasis will be placed on the social and gender inequalities associated with various forms of work-related high mobility. Based on the JobMob data, we will first show that the portion of the population practising high mobility (when measured by travel time) has been stable over the past decades rather than increasing. Young highly mobile people have nevertheless more fluctuating early-career mobility histories than their elders did at the same stage in their career. People frequently start and stop being highly mobile over their careers. These changes are often unpredictable for actors and depend on the economic climate and the personal context. While middle-class people are more likely to become highly mobile than working-class people, they are not more likely to practise high mobility in the long run. Secondly, we will show that there is a considerable variety in the opinions of highly mobile people regarding their situation. Some people find pleasure and professional opportunities in high mobility. In Spain, for example, low-income mobile people tend to see high mobility more positively in times of economic crisis, because it helped them to get or keep a job. Overall, we observed a normalisation process over mobile people’s lives. People increasingly see their mobility as a need enabling them to combine a distant job with a local place attachment. However, some social groups face major difficulties in combining high mobility demands and family development. Single parents are often under time pressure, which results in a negative perception of their long commutes. Women living in Germany and Switzerland who have a job requiring frequent/long-distance travel are less likely than their male counterpart to stay with the same partner and to have children. We conclude by suggesting some possible policy interventions.

International audience; This chapters examines the ways highly mobile people are formed by high mobility, that is acquire the skills, practices and values of high mobility, and transformed through the experience of high mobility, that is change their skills, practices and values previously acquired. We draw here on the notion of socialisation defined as formation and transformation (Darmon, 2006) to investigate this process. We first define the concept of socialisation and situate it in the sociological tradition. We then explore the role of primary (childhood) and secondary (adulthood) socialisation to high mobility. We finally discuss the ways these two types of socialisation influence how highly mobile people experience, feel and plan for the future their mobility.We show two different attitudes towards mobility experiences during childhood and within the family (primary socialisation). For some, high mobility appears to be a continuation of childhood mobility experiences. Others, however, reject the mobility practices to which they were exposed early in life. Concerning secondary socialisation, we show that, for some people, certain mobility experiences, such as travel or job training, serve more or less as direct preparation for high mobility.For others, preparation for high mobility occurs through practice, with greater or lesser degrees of success.